Subject: kern/18958: uvm_loan users use kernel_object-backed VM ranges
To: None <email@example.com>
From: None <firstname.lastname@example.org>
Date: 11/06/2002 22:09:17
>Synopsis: uvm_loan users use kernel_object-backed VM ranges
>Arrival-Date: Wed Nov 06 22:10:03 PST 2002
>Originator: Jason R Thorpe
>Release: NetBSD 1.6I
Wasabi Systems, Inc.
System: NetBSD yeah-baby.shagadelic.org 1.6I NetBSD 1.6I (YEAH-BABY-XP) #11: Sun Sep 29 17:42:25 PDT 2002 email@example.com:/u1/netbsd/src/sys/arch/i386/compile/YEAH-BABY-XP i386
Users of uvm_loan() tend to use uvm_km_valloc() or
uvm_km_valloc_wait() to allocate the KVA at which
loaned pages will be mapped.
This is not a problem with basic functionality, but can
cause interesting behavior in the face of other bugs, since
a write fault will cause UVM to COW'd (overwriting the k-mapping
with a non-k-mapping), which will cause a panic later, at some
This was diagnosed by Chuq Silvers.
See the audit trail of kern/18809.
Provide a uvm_km_*alloc() routine which creates a backed-